System and method for controlling a tracking servo during label printing

ABSTRACT

A visible light characteristic changing layer formed from photosensitive or heat-sensitive material is formed in a location which can be viewed from a part of a label surface of an optical disk. The optical disk is set on a turntable of an optical disk unit while the label surface of the optical disk is directed downward. The optical disk and an optical pickup are moved mutually along the plane of the optical disk. In synchronism with the relative movement, the power of a laser beam output from the optical pickup is modulated in accordance with image data, such as characters or graphic images to be printed, and the laser beam is emitted onto the visible light characteristic changing layer. As a result of the visible light characteristic changing layer being exposed to the laser beam, a visible-light reflectivity of the visible light characteristic changing layer is changed, thereby forming a image corresponding to the image data on the label surface.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 10/053,238,filed Oct. 29, 2001, the entire disclosure of which is herein expresslyincorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a method of printing a label providedon an optical disk, to an optical disk unit, and relates to an opticaldisk in which a label can be subjected to printing by utilization of alaser beam output from an optical disk unit.

In a recordable optical disk, information about contents recordedthereon (e.g., titles) is described on an optical disk by a user so thatthe recorded contents can be checked visually. In the case of asingle-sided optical disk which is handled as a single disk withoutbeing housed in a cartridge, such as a CD-system optical disk i.e., aCD-R (CD recordable), a CD-RW (CD rewritable), etc. the information isusually written directly on a label surface of the optical disk with apen. According to another method, information about recorded contentsrecorded are edited on a personal computer, and the contents are printedon a label with a printer. The label is then pasted to the labelsurface.

According to the method in which contents are written directly on thelabel surface of the disk, a recording layer is often damaged by astrong writing action effected by use of a stiff pencil. According tothe method of printing a label with a printer, there is a necessity forusing a printer.

SUMMARY OF THE INVENTION

The present invention has been conceived in light of the foregoingproblem and aims at providing a method of forming an image on a labelsurface of an optical disk, an optical disk unit, and an optical disk,wherein an image is formed on a label surface of an optical disk byutilization of a laser beam output from an optical disk unit, therebyobviating a necessity for writing of an image performed with a pen orprinting an image with a printer.

The present invention provides a method of forming an image on a labelsurface of an optical disk, the method comprising the steps of: forminga visible light characteristic changing layer in a position which can beviewed from a label surface side of an optical disk, the layer changinga characteristic of visible light having entered from the label surfaceside by exposure to a laser beam used for recording a signal and emittedfrom the part of the label surface; setting the optical disk on aturntable of an optical disk unit such that a label surface of theoptical disk is oriented toward a direction in which a laser beamemitted from an optical pickup is to enter; relatively moving theoptical disk and the laser beam along a plane of the optical disk; andmodulating the laser beam, in synchronism with the mutual movement, intoa specific characteristic in accordance with image data to be printed,such as characters or graphic images, and emitting the modulated laserbeam onto the visible light characteristic changing layer from the partof the label surface, wherein a reflection characteristic of the visiblelight having entered the visible light characteristic changing layer ischanged by means of exposure, thereby printing a corresponding image onthe label surface. According to the label surface image formationmethod, a laser beam output from the optical disk unit can be emittedonto the visible light characteristic changing layer formed in an areawhich can be viewed from the part of a label surface of an optical disk,thereby changing the reflectivity, permeability, or light-scatteringcharacteristic of the visible light. In this way, corresponding images,such as characters or graphic images, can be formed on the labelsurface, thereby obviating a necessity of writing images with a pen orprinting images with a printer.

Under the method according to the present invention, the laser beam usedfor recording a signal can be a laser beam of predetermined power orhigher. The optical pickup can be moved in a radial direction of theoptical disk while the optical disk is being rotated. The optical diskcan be made stationary, and the optical pickup is moved in a radialdirection of the optical disk as well as in a direction which isorthogonal to the radial direction of the optical disk and is tangent toa track.

The present invention also provides an optical disk unit comprising: arelative movement mechanism for relatively moving an optical disk set ona turntable while a label surface is oriented in a direction in which alaser beam is to enter, and a laser beam emitted from an optical pickupalong a plane of the optical disk; a laser modulation circuit formodulating a laser beam emitted from the optical pickup; and a circuitfor controlling the relative movement mechanism and the laser modulationcircuit, wherein the control circuit performs control operation so as toform an image on a visible light characteristic changing layer bycontrolling the relative movement mechanism to relatively move theoptical disk and the laser beam and controlling the laser modulationcircuit in accordance with image data, such as characters or graphicimages, to be formed on a label surface of the optical disk, therebymodulating a laser beam output from the optical pickup on the basis ofthe image data, and thereby forming an image corresponding to the imagedata on the visible light characteristic changing layer, acharacteristic of reflectivity, permeability or light scattering of thevisible light is changed by the exposure of the laser beam, which can beviewed from the part of a label surface of the optical disk. The opticaldisk unit enables implementation of the label surface image formationmethod according to the present invention.

Preferably, the relative movement mechanism includes a rotary drivedevice for rotationally driving a turntable and a radial-direction feeddrive device for moving the optical pickup in a radial direction of theoptical disk; wherein the control circuit can control the rotary drivedevice and the radial-direction feed drive device, thereby controllingrelative movement between the optical disk and the laser beam. In thiscase, the control circuit can drive the rotary drive device to aconstant rotating speed, thereby driving the radial-direction feed drivedevice by a predetermined amount at each predetermined rotary position.Further, the optical disk unit can further comprise acircumferential-direction position sensor for detecting acircumferential position on the optical disk, and a radial-directionposition sensor for detecting a radial position of the optical pickup onthe optical disk; wherein the control circuit can perform a controloperation for modulating a laser beam emitted from the optical pickup,in accordance with the position detected by thecircumferential-direction position sensor and the radial-directionposition sensor and with image data to be formed on a label surface ofthe optical disk, such as characters or graphic images. The positionalinformation about image data can be expressed as coordinate dataconsisting of a combination of a circumferential position on an opticaldisk and a radial position on an optical disk. Thecircumferential-direction position sensor can comprise a frequencygenerator which is rotated by the rotary drive device to generate asignal of frequency corresponding to rotation, and a multiplier formultiplying the frequency of a signal generated by the frequencygenerator. The relative movement mechanism can comprise aradial-direction feed drive device for moving the optical pickup in aradial direction of the optical disk, and a track-tangential-directionfeed drive device for moving the optical pickup in a direction which isperpendicular to the radial direction of movement and is tangent to atrack of the optical disk; wherein the control circuit can controlrelative movement between the optical disk and the laser beam bycontrolling the radial-direction position sensor and thetrack-tangential-direction feed drive device while the turntable is leftin a stationary state. The optical disk unit further comprises acircumferential-direction position sensor for detecting acircumferential position on the optical disk, and atrack-tangential-direction position sensor for detecting a positionwhich is orthogonal to the radial direction of movement and is tangentto a track of the optical disk; wherein the laser beam emitted from theoptical pickup can be controlled in accordance with the positiondetected by the circumferential-direction position sensor and thetrack-tangential-direction position sensor and with image data to beformed on a label surface of the optical disk, such as characters orgraphic images. The positional information about image data can beexpressed as coordinate data consisting of a combination of a radialposition on an optical disk and a position along a direction which isperpendicular to the radial direction of movement of the optical diskand is tangent to a track of the optical disk. Further, the controlcircuit performs relative movement between the optical disk and thelaser beam by turning off a tracking servo and turning on/off a focusservo. The control circuit can perform a control operation for vibratingand driving a tracking actuator of the optical pickup while performingrelative movement between the optical disk and the laser beam. Theoptical disk unit according to the present invention can be embodied in,for example, an optical disk unit for a single-side CD-type opticaldisk, such as a CD-R (CD-R recordable) and CD-RW (CD rewritable); or anoptical disk recording device for an optical disk formed by laminatingtwo substrates; for example, a DVD-type optical disk such as a DVD-R(DVD recordable) or DVD-RW (DVD rewritable).

The present invention also provides an optical disk comprising a visiblelight characteristic changing layer which changes a visiblecharacteristic of a visible light by exposure to a laser beam havingentered from a label surfaces and which is formed in a location capableof being viewed from the part of the label surface. The optical diskenables implementation of the label surface image formation methodaccording to the present invention. Since the visible lightcharacteristic changing layer is formed integrally on an optical disk,occurrence of vibration caused by mass eccentricity during high-speedrotation, and occurrence of failure caused by exfoliation of a labelwithin a drive can be prevented, as compared with a label pastingmethod.

Preferably, the visible light characteristic changing layer can beembodied in a color-changing layer which undergoes fading, coloring, orchanges in color or hue by exposure to the laser beam. Further, thecolor-changing layer can be embodied in a photosensitive or heatsensitive layer, or two layers construction. In case of the two layersconstruction, the two layers are fused or mixed together by exposure tothe laser beam, thereby changing a visible-light characteristic. Theoptical disk can be constituted by sequentially forming, on a substrate,at least a recording layer, a reflection layer, and a protective layer;and the visible light characteristic changing layer can be formedbetween the reflection layer and the protective layer. An intermediatelayer can be disposed between the reflection layer and the visible lightcharacteristic changing layer, in order to improve, for example,adhesion between a reflection layer and a visible light characteristicchanging layer, and to effect insulation control for the purpose ofcontrolling heat conductivity contributing to changes in acharacteristic of visible light or protecting data recorded on arecording surface of an optical disk, the reflection layer and theintermediate layer can be joined directly together, and the intermediatelayer and the visible light characteristic changing layer can be joineddirectly together. The interface between the reflection layer and theprotective layer can be formed so as to be a fine mixture of a partcontaining the visible light characteristic changing layer and a partwhich does not include the visible light characteristic changing layerand is joined directly to the reflection layer and to the protectivelayer. Since the optical disk has a part where the reflection layer andthe protective layer are joined directly together, adhesion can beimproved and there can be realized control of thermal conductivityattributable to changes in a visible light characteristic. Even when thevisible light characteristic changing layer is translucence, thereflection layer can be partially viewed from the label surface side viathe part where no visible light characteristic changing layer is presentand the reflection layer and the protective layer are joined togetherdirectly. Focus can be readily achieved on the reflection layer at thetime of formation of an image on the label surface. The structure inwhich there are finely mixed together a part containing the visiblelight characteristic changing layer and a part which does not includethe visible light characteristic changing layer and is joined directlyto the reflection layer and to the protective layer can be embodied in astructure in which the visible light characteristic changing layer isformed between the reflection layer and the protective layer in the formof a plurality of dots or a plurality of voids. The visible lightcharacteristic changing layer can be constituted in the form ofconcentric fringes or linear stripes, rather than in the form of dots orvoids. The optical disk according to the present invention can beembodied in, for example, an optical disk unit for a single-side CD-typeoptical disk, such as a CD-R (CD-R recordable) or CD-RW (CD rewritable);or an optical disk recording device for an optical disk formed bylaminating two substrates; for example, a DVD-type optical disk such asa DVD-R (DVD recordable) or DVD-RW (DVD rewritable).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross section showing an embodiment of an opticaldisk according to the present invention;

FIG. 2 is a partial cross section showing a modification of the opticaldisk shown in FIG. 1;

FIG. 3 is a partial cross section showing another modification of theoptical disk shown in FIG. 1;

FIG. 4 is a partial cross section showing yet another modification ofthe optical disk shown in FIG. 1;

FIG. 5 is a partial cross section showing another embodiment of theoptical disk according to the present invention;

FIG. 6 is a system configuration block diagram showing an embodiment ofan optical disk unit according to the present invention;

FIG. 7 is a plan view showing the locus of movement of a laser beam on alabel surface stemming from an operation for subjecting the labelsurface to printing through use of a CD-R/RW drive shown in FIG. 6;

FIG. 8 is a timing chart showing changes in laser power which ariseduring the course of the printing operation shown in FIG. 7;

FIG. 9 is a plan view showing the locus of movement of a laser beam overa label surface arising when printing is effected without vibrating thelaser beam in a radial direction of the optical disk;

FIG. 10 is a plan view showing the locus of movement of a laser beamover a label surface arising when printing is performed while vibratingthe laser beam in a radial direction of the optical disk;

FIGS. 11A and 11B are a plan view and an enlarged partial plan viewshowing an example of a print made on the label surface by means of theCD-R/RW drive shown in FIG. 6;

FIGS. 12A to 12C are plans view showing another example of a print madeon the label surface by means of the CD-R/RW drive shown in FIG. 6;

FIG. 13 is a system configuration block diagram showing anotherembodiment of the optical disk unit according to the present invention;

FIGS. 14A and 14B are plan and front views showing an example layout ofthe CD-R/RW drive feed mechanism shown in FIG. 13;

FIGS. 15A and 15B are plan and front views showing the example layout ofthe CD-R/RW drive feed mechanism shown in FIG. 13;

FIG. 16 is a plan view showing an example of a print product formed onthe label surface by means of the CD-R/RW drive shown in FIG. 13.

FIG. 17 is a partial cross section showing another modification of theoptical disk shown in FIG. 1;

FIG. 18 is a partial cross section showing another modification of theoptical disk shown in FIG. 1; and

FIG. 19 is a partial cross section showing another modification of theoptical disk shown in FIG. 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention will be described hereinafter. FIG.1 is a partial cross section (the thickness of each layer differs fromthat of an actual layer, and a guide groove is omitted from the drawing)showing an optical disk according to the embodiment of presentinvention. The embodiment shows an example in which the presentinvention is applied to a CD-R disk. As to optical disk 10, a pigmentlayer (i.e., a recording layer) 14, a reflection layer 16, a visiblelight characteristic changing layer 18 and a protective layer 20 aresequentially formed on a single side of a transparent substrate so as toconstitute the optical disk 10. The optical disk 10 is identical with anordinary CD-R disk, except for provision of the visible lightcharacteristic changing layer 18. The visible light characteristicchanging layer 18 can be seen through a transparent protective layer 20from a label surface 22. The reflectivity, permeability, oroptical-scattering characteristic (i.e., reflectivity, permeability, andspectrum light scattering) in an area of the visible lightcharacteristic changing layer 18 is changed when the area of the layer18 is exposed to a laser beam having predetermined power or more fromthe label surface 22 side. The visible light characteristic changinglayer 18 can be formed from a material layer (i.e., a color changinglayer, a photosensitive layer, or a heat sensitive layer) which changesin color, such as a photo-sensitive material or heat-sensitive material,e.g., change from white to color (e.g., black) or from transparent tocolor (e.g., black). When the visible light characteristic changinglayer 18 is formed from a photosensitive layer, there can be employedphotosensitive material which is not photosensitized by the laser havingpower of less than 1 mW, but is photosensitized to discolor thephotosensitive layer by a laser beam of 780 nm having power of 1 mW ormore, with respect to a laser beam of 780 nm from the laser surface 22side. When the visible light characteristic changing layer 18 is formedfrom a heat-sensitive layer, there can be employed heat sensitivematerial which is not sensitive to a heat of less than 100° C. butbecomes sensitive to heat of 100° C. or higher to discolor the heatsensitive material. Further, the color-changing layer may be provided asthe visible light characteristic changing layers. The color-changinglayer is formed from two layers which are fused or mixed together bybeing exposed to the laser beam, thereby changing a visible-lightcharacteristic. Since the laser beam for recording and playing the backdata of the optical disk 10 is entered from the substrate 12 side and sothat the laser beam is substantially cut off by the reflection layer 16.Therefore, the visible light characteristic changing layer 18 does notcause any change in the visible-light characteristic of the laser beam.

As shown in FIG. 2, an intermediate layer 24 can be provided between thereflection layer 16 and the visible light characteristic changing layer18. The intermediate layer 24 can improve adhesion between a reflectionlayer and a visible light characteristic changing layer, control heatconductivity contributing to changes in a characteristic of visiblelight, and control heat insulating property to protect data recorded ona recording surface of an optical disk. The reflection layer and theintermediate layer can be joined directly together, and the intermediatelayer and the visible light characteristic changing layer can be joineddirectly together. As shown in FIG. 3, in place of the intermediatelayer 24, the visible light characteristic changing layer 18 is formedinto a structure having a plurality of minute dots (e.g., each assuminga circular shape having a diameter of tens of micrometers or anon-circular shape of similar size), through use of, e.g., a filmtransfer technique. Alternatively, in place of a plurality of minutepores, the visible light characteristic changing layer 18 can be formedinto a porous structure having a plurality of minute pores 26. In a casewhere the visible light characteristic changing layer 18 is formed intothe structure having dots such as shown in FIG. 3, the reflection layer16 and the protective layer 20 are joined together directly outside thedots. In a case where the visible light characteristic changing layer 18is formed into the structure having pores such as that shown in FIG. 4,the reflection layer 16 and the protective layer 20 are directly joinedtogether within the pores. As a result, there can be achieved goodadhesion, and heat insulation control can be performed for the purposeof attaining the object. Even when the visible light characteristicchanging layer 18 is translucence, the reflection layer 16 can bepartially seen from the part of the label surface 22, through an areawhere no visible light characteristic changing layer 18 is present andat which the reflection layer 16 and the protective layer 20 are joinedtogether directly. At the time of printing of the label surface 22,focusing on the reflection layer 16 can be achieved readily. The visiblelight characteristic changing layer 18 can be made into a structurehaving concentric fringes or linear stripes.

As shown in FIG. 19, a light scattering layer 24 (a translucenceintermediate layer) may be provided between the visible lightcharacteristic changing layer 18 and the reflection layer 16. Byproviding the translucence intermediate layer 24, light, which passesthrough the visible light characteristic changing layer 18 and isreflected by the reflection layer 16, is not directly emitted from thesurface of the optical disk. That is, the light, which passes throughthe visible light characteristic changing layer 18, is scattered by thetranslucence intermediate layer 24. Therefore, light from the opticaldisk can be controlled by adjusting the translucence intermediate layer24, so that the various type of images can be formed on the surface ofthe optical disk as label.

FIG. 5 is a partial cross section (the thickness of each layer differsfrom that of an actual layer, and a guide groove is omitted from thedrawing) showing another embodiment of the optical disk according to thepresent invention. This embodiment is an example in which the presentinvention is applied to a CD-RW disk. As to an optical disk 28, adielectric layer 32, a recording layer 34, a dielectric layer 36, areflection layer 38, a visible light characteristic changing layer 40,and a protective layer 42 are sequentially formed on a single of atransparent substrate 30 made of, for example, polycarbonate so as toconstitute the optical disk 28. The optical disk 28 is identical with anordinary CD-RW disk, except for provision of the visible lightcharacteristic changing layer 40. The visible light characteristicchanging layer 40 can be seen from a label surface 44 side through atransparent protective layer 42. The visible light characteristicchanging layer 40 can be constituted in the same manner as in thevisible light characteristic changing layer 18 shown in FIG. 1. As inthe case of the optical disk 10 shown in FIG. 2, an intermediate layercan be interposed between the reflection layer 38 and the protectivelayer 42 for the purpose set forth. Further, the visible lightcharacteristic changing layer 40 can be formed into a structure having aplurality of minute spots, as in the visible light characteristicchanging layer 18 shown in FIG. 3. Alternatively, the visible lightcharacteristic changing layer 40 can be formed into a porous structurehaving a plurality of minute pores, as shown in FIG. 4. As anotheralternative, the visible light characteristic changing layer 40 can beformed into a structure having concentric fringes or a structure havinglinear stripes.

FIG. 17 shows a partial cross section (the thickness of each layerdiffers from that of an actual layers, and a guide groove is omittedfrom the drawing) showing another embodiment of the optical diskaccording to the present invention. In this embodiment, a reflectionlayer for data recording and a reflection layer for imaging a label areseparately provided in the optical disk. That is, a second reflectionlayer 35 is formed between an intermediate layer 35 and a buffer layer37 (separation layer) as shown in FIG. 17. The second reflection layer35 is made of metal or derivative reflection material. Remain portion ofthe optical disk shown in FIG. 17 is identical to the optical disk shownin FIG. 5. In this embodiment, since the reflection layers 35 and 38 areseparately provided in the optical disk, mutual influence of recordingdata and printing label to the visible light characteristic changinglayer 40 and the recording layer 34 is reduced. Therefore, the influenceon formation of an image on the label surface is certainly eliminated.

FIG. 18 shows a partial cross section (thick ness of each layer differsfrom that of an actual layers, and a guide groove is omitted from thedrawing) showing another embodiment of the optical disk according to thepresent invention. This embodiment is an example in which the presentinvention is applied to an optical disk comprising two substratesadhered with other, such as a DVD (Digital video Disk). The optical diskin this embodiment is constituted as follows: a dielectric layer 32, arecording layer 34, a dielectric layer 36 and a first reflection layer38 are sequentially formed on a first transparent substrate; a secondreflection layer 35 made of metal or derivative reflection material, atranslucence intermediate layer 39 (a light scattering layer), a visiblelight characteristic changing layer 40 and a protective layer 42 aresequentially formed on a second substrate 33; and the second substrate33 is built on the first substrate 30 through a laminating adhesivelayer 31 as shown in FIG. 18. In case of DVD, each substrate has athickness of 0.6 mm and is laminated each other, so that sum ofthickness including a recording layer is 1.2 mm.

FIG. 6 shows an embodiment of the optical disk unit according to thepresent invention (showing only the portions of the unit pertaining toprinting of a label surface). The optical disk unit is configured as aCD-R/RW drive (an optical disk drive which enables recording andreproduction of data on and from a CD-R disk and a CD-RW disk) used withconnection with a host computer 46, such as a personal computer. Anoptical disk 50 according to the present invention (the CD-R disk shownin FIGS. 1 through 4 or the CD-RW disk 28 shown in FIG. 5, etc.) isplaced on a turn-table 54 while being inverted (i.e., a label surface 52is turned down) and the optical disk 50 is driven to be rotated. Afrequency generator (FG) 58 is directly connected to a rotary shaft of aspindle motor 56. The frequency generator 58 generates a pulse signal(FG pulse) for each turning angle, the turning angle being determined bydividing one rotation of the spindle motor 56 by a predeterminedinteger. The FG pulse signal is multiplied by a predetermined number bya multiplier 60 constituted by a PLL circuit. The thus-multiplied FGpulse is input to a system control circuit (CPU) 62, where the signal isused for detecting a peripheral position. At the time of printing of alabel surface, a spindle servo circuit 64 controls, on the basis of theFG pulse signal, the spindle motor 56 so as to rotate constantly at arotating speed instructed by the system control circuit 62.

An optical pickup 66 is provided at a position under the optical disk 50for executing recording and reproduction of data and printing of alabel. The optical pickup 66 is supported by a feed screw 68 so as to beable to move in the radial direction of the optical disk 50. A feedmotor 72 is driven by a motor driver 70 in accordance with aninstruction output from the system control circuit 62 so as to rotatethe feed screw 68 so that the optical pickup 66 is moved in the radialdirection of the optical disk 50. A feed position sensor 74, such as alinear scale, detects the radial position of the optical pickup 66 onthe optical disk 50. In accordance with an instruction output from thesystem control circuit 62, a focus servo circuit 76 actuates a focusactuator of the optical pickup 66 on the basis of a focus error signal,thus executing focus control operation. At the time of printing a label,the focus servo circuit 76 is turned on. At the time of recording orreproduction of data, a tracking servo circuit 78 actuates a trackingactuator of the optical pickup 66 on the basis of a tracking errorsignal in accordance with the instruction output from the system controlcircuit 62, thus executing tracking control operation. At the time ofprinting a label, the tracking servo circuit 78 is turned off. At thetime of printing a label, a vibration signal generation circuit 80generates a predetermined vibration signal in accordance with theinstruction output from the system control circuit 62, and supplies thevibration signal to the tracking actuator. Accordingly, an object lensof the optical pickup 66 is vibrated in the radial direction of theoptical disk 50 to thereby bridge a gap between the areas circularlyscanned by a laser beam, as a result of which there is obtained a printproduct having no gaps.

The laser driver 82 drives a laser diode of the optical pickup 66 toemit a laser beam onto the optical disk 50 in accordance with theinstruction output from the system control circuit 62, thereby executingrecording/reproduction of data or printing a label. At the time ofrecording of data, the laser diode outputs a laser beam of recordingpower modulated by a recording signal. At the time of reproduction ofdata, the laser diode outputs a laser beam of fixed reproduction power.At the time of printing label, the laser diode outputs a laser beammodulated based on image data pertaining to characters or graphic imagesto be printed (i.e., a laser beam has high power so as to cause changesin the visible light characteristic changing layer in an area to beprinted and a laser beam has low power so as not to cause changes in thevisible light characteristic changing layer in an area not to beprinted). At the time of printing a label, the host computer 46transmits, to a CD-R/RW drive 48, image data, which edited by a user andto be printed, pertaining to characters or graphic images. The imagedata is constituted by data (e.g., data which specify a print segmentrepresented by an angle θ for each radial position “r” at apredetermined pitch Δr) represented by coordinates (r, θ), thecoordinates corresponding to a combination of a radial position “r” ofan optical disk (a distance from a rotation center) and acircumferential position θ (a circumferential angle relative to anappropriate reference position).

Process of printing data on a label surface of the optical disk 50 bythe CD-R/RW drive 48 shown in FIG. 6 is performed in the mannerdescribed below.

(1) The optical disk 50 is set on the turntable 54 while being invertedin case of recording data or reproducing, i.e. the optical disk 50 isset so as to face the surface of the optical disk 50, which the label isto be printed, to the optical pick up 66.

(2) A user edits, on a display of the host computer 46, characters or agraphic image such as a picture to be printed. The host computer 46converts the thus-edited image into image data.

(3) The user instructs to start printing operation on the host computer46.

(4) The spindle servo circuit 64 subjects the spindle motor 56 to CAV(constant rotating speed) control so that the pulse generated by thefrequency generator 58 is to be a fixed frequency instructed by thesystem control circuit 62.

(5) The optical pickup 66 is positioned at a predetermined radialreference position at the inner radius of the optical disk 50.

(6) The laser driver 82 drives the laser diode so that the laser powerof a laser diode of the optical pickup 66 is to be a predetermined lowoutput instructed by the system control circuit 62 (a value of whichenables focus control operation without involvement of occurrence ofchanges in the visible light characteristic changing layer: e.g., avalue of 1 mW or less).

(7) The focus servo circuit 76 is turned on in accordance with theinstruction output from the system control circuit 62. Then, the focusservo circuit 76 executes focus servo operation so that the laser beam67 forms the minimum spot on the reflection layer. Here, the trackingservo circuit 78 remains off, and no tracking servo operation isperformed.

(8) Through the foregoing operations, preparation for printing is made,and printing is commenced in accordance with the instruction output fromthe system control circuit 62. That is, the system control circuit 62receives image data from the host computer 46, then, drives the feedmotor 72 to position the optical pickup 66 in a radial position at theinner radius of the optical disk 50, where a first print location ispresent. While appropriate timing based on the FG pulse signal (or adetection timing for a sensor additionally provided for detecting areference circumferential position) is taken as a circumferentialreference position, a circumferential position θ is detected by countinga pulse signal output from the multiplier 60 is counted. With respect tothe radial position on the disk, laser power is switched to apredetermined high output (a value at which changes arise in the visiblelight characteristic changing layer; for example, a value of 1 mW ormore) in each circumferential print position instructed on the basis ofimage data. As a result, changes (i.e., discoloration) arise in thereflection characteristic changing layer at the location exposed to thelaser beam of high output power, thereby performing printing operation.When the optical disk 50 returns to the circumferential referenceposition after having effected one rotation, the feed motor 62 isactuated so as to move the optical pickup 66 toward an outercircumference at a predetermined pitch Δr, and then, with respect to theradial position on the disk, laser power is switched to a predeterminedhigh output in each circumferential print position instructed on thebasis of image data. This printing operation is repeated to print sothat the optical pickup 66 is sequentially moved toward the outercircumference at the predetermined pitch Δr every one rotation. FIG. 7shows the locus of movement of the laser beam over the label surface 52of the optical disk 50 through the printing operation. In the areadesignated with thick lines, the laser power of the laser beam isswitched to high power, thereby performing printing operation. FIG. 8shows variations in the laser power of the laser beam when the printingoperation shown in FIG. 7 is performed.

Scanning is not performed at radial positions where there is no printarea, and, the optical pickup 66 moves to a radial position where thenext print area is present by passing through the radial position havingno print area, and printing is performed. If the pitch Δr is large, animage which is originally to be printed without interruption in theradial direction is printed with gaps, as shown in FIG. 9. In contrast,if the pitch Δr is made small, gaps can be made unnoticeable. However,the number of rotations required for printing data on the entire labelsurface is increased, and printing involves consumption of time. Forthis reason, the CD-R/RW drive 48 drives a tracking actuator with avibration signal (e.g., a sinusoidal signal or triangular signal)generated by the vibration signal generation circuit 80 during aprinting operation, thereby vibrating the objective lens in the radialdirection of the optical disk 50. As shown in FIG. 10, the laser beam isvibrated in the radial direction of the optical disk 50, therebyenabling a printing operation without gaps (or with occurrence of smallgaps) even at a comparatively large pitch Δr. The frequency of thevibration signal can be set to, e.g., several kilohertz or thereabouts.Further, the pitch Δr can be set to, e.g., 50 to 100 μm or thereabouts.

FIG. 11A shows a practical example of a print made on the label surface52 by the CD-R/RW drive 48. FIG. 11B shows a partial enlarged viewshowing the locus of movement of a laser beam used during printing ofthe print example. The drawing shows that, when scanning in a radialposition r1 is performed, the laser power of the laser beam is increasedwithin an angular segment from θ1 to θ2. FIGS. 12A through 12C showother examples of print products made on the label surface 52 by theCD-R/RW drive 48. Arbitrary character information, such as disk titles,music titles, the names of artists, or pictures can be printed.

FIG. 13 shows another embodiment of the optical disk unit according tothe present invention (showing only the elements contributing toprinting of a label surface). In a CD-R/RW drive 84, the optical disk 50(the CD-R disk 10 shown in FIG. 10 or the CD-RW disk 28 shown in FIG. 5)according to the present invention is set on a turntable 86 while beinginverted (i.e., while the label surface 52 is turned down). At the timeof printing operation, the spindle motor 88 is not driven. An opticalpickup 90 for performing recording or reproduction of data is providedat a location under the optical disk 50. The optical pickup 90 issupported by a feed screw 92 so as to be movable in the radial directionof the optical disk 50. In accordance with the instruction output fromthe system control circuit 62, a feed motor 94 is driven by a motordriver 96, thereby rotating the feed screw 92 so that the optical pickup90 is moved in the radial direction of the optical disk 50. The radialdirection position of the optical pickup 90 on the optical disk 50 isdetected by a feed position sensor 98 such as a linear scale.

The entirety of the disk radial feed mechanism having the feed screw 92and the feed motor 94 is movably supported by a feed screw 101 disposedin parallel with the plane of the disk 50 perpendicular to the feedscrew 92, so as to be movable in the direction tangent to a track (i.e.,a direction perpendicular to a feed direction in the radial direction ofthe disk). In accordance with an instruction output from a systemcontrol circuit 105, a feed motor 103 is driven by a motor driver 107 soas to rotate the feed screw 101. As a result, the optical pickup 90 ismoved in the direction tangent to a track. The position of the opticalpickup 90 in the direction tangent to a track is detected by a feedposition sensor 109 such as a linear scale.

FIGS. 14A and 14B show a layout of a feed mechanism (neither a feedmotor nor a feed screw is shown) as example. Slide bars 111 are providedin and fixed to a mechanical base of the CD-R/RW drive 84 in parallelwith the plane of the optical disk 50. An optical pickup unit 113 isslidably supported on the slide bar 111. The optical pickup unit 113 ismoved along the slide bars 111 by the feed motor 103 and the feed screw101 (shown in FIG. 13). Slide bars 115 are mounted on and fixed to theoptical pickup unit 113 in parallel with the plane of the optical disk50 and perpendicular to the slide bars 111. The optical pickup 90 isslidably supported by the slide bars 115 and is moved along the slidebars 115 by the feed motor 94 and the feed screw 92 (shown in FIG. 13).At the time of printing operation, feed mechanisms feeding in twodirections are driven. At the time of recording/reproduction of data,only the mechanism feeding operation in the radial direction of a track(simply a “track-radial-direction feed mechanism”) is driven, and themechanism feeding in the direction tangent to a track (simply a“track-tangential-direction feed mechanism”) is stopped in a neutralposition thereof (i.e., the position in which an objective lens 90 a ofthe optical pickup 90 is moved in the radial direction of a disk bydriving the track-radial-direction feed mechanism).

The track-tangential-direction feed mechanism can move the spindle motor88 instead of moving the optical pickup 90. In this case, a feed screw117 and a feed motor 119 for moving the spindle motor 88 in the samedirection are provided in place of the feed screw 101 and the feed motor103 for moving the optical pickup 90 in the direction tangent to atrack. FIGS. 15A and 15B show a layout of the feed mechanism in such acase (neither the feed motor 119 nor the feed screw 117 is shown) as anexample. Slide bars 121 are provided in and fixed to a mechanical baseof the CD-R/RW drive 84 in parallel with the plane of the optical disk50. A spindle motor 88 is slidably supported by the slide bars 121. Thespindle motor 88 is moved along the slide bars 121 by a feed motor 119and a feed screw 117 (see FIG. 13). Slide bars 123 are mounted on andfixed to a mechanical base of the CD-R/RW drive 84. The optical pickup90 is slidably supported by the slide bars 123 and is moved along theslide bars 123 by the feed motor 94 and the feed screw 92 (shown in FIG.13). At the time of printing operation, feed mechanisms feeding in twodirections are driven. At the time of recording/reproduction of data,only the track-radial-direction feed mechanism is driven. Thetrack-tangential-direction feed mechanism is stopped in a neutralposition thereof (i.e., the position in which an objective lens 90 a ofthe optical pickup 90 is moved in the radial direction of a disk bydriving the track-radial-direction feed mechanism).

In FIG. 13, in accordance with an instruction output from the systemcontrol circuit 105, a focus servo circuit 125 actuates a focus actuatorof the optical pickup 90 on the basis of a focus error signal, thusperforming focus control operation. At the time of printing a label, thefocus servo circuit 125 is turned on. At the time of recording orreproduction of data, a tracking servo circuit 127 actuates a trackingactuator of the optical pickup 90 on the basis of a tracking errorsignal in accordance with the instruction output from the system controlcircuit 105, thus performing tracking control operation. At the time ofprinting a label, the tracking servo circuit 127 is turned off. At thetime of printing a label, the vibration signal generation circuit 129generates a predetermined vibration signal in accordance with theinstruction output from the system control circuit 105, and supplies thevibration signal to the tracking actuator. Accordingly, an object lensof the optical pickup 90 is vibrated in the radial direction of theoptical disk to bridge a gap between the areas circularly scanned by alaser beam, as a result of which there is obtained a print producthaving no gaps.

In accordance with the instruction output from the system controlcircuit 105, a laser driver 131 drives a laser diode of the opticalpickup 66 to emit a laser beam onto the optical disk 50, therebyperforming recording/reproduction of data or printing of a labelsurface. At the time of recording of data, the laser diode outputs alaser beam of recording power modulated by a recording signal, bydriving action of the laser driver 131. At the time of reproduction ofdata, the laser diode outputs a laser beam whose recording power has afixed predetermined reproducing power. At the time of printing label,the laser diode outputs a laser beam modulated with image datapertaining to characters or graphic images to be printed (i.e., a laserbeam has high power to cause changes in the visible light characteristicchanging layer in an area to be printed and a laser has low power so asnot to cause changes in the visible light characteristic changing layerin an area not to be printed). At the time of printing a label, a hostcomputer 133 transmits, to the CD-R/RW drive 84, image data pertainingto characters or graphic images to be edited by the user and to beprinted. The image data are constituted by dot-matrix data (e.g., datawhich specify a print segment in the direction tangent to a trackrepresented by “t,” for each radial position “r” at a predeterminedpitch Δr) represented by coordinates (r, t), the coordinatescorresponding to a combination of a radial position “r” of an opticaldisk, which is a distance from an appropriate reference position (e.g.,rotation center) in the radial direction of the disk, and a position “t”in the direction tangent to a track, which is a distance from theappropriate reference position in the direction tangent to a track.

Process of printing data on a label surface of the optical disk 50 bythe CD-R/RW drive 84 shown in FIG. 13 is performed in the mannerdescribed below.

(1) The optical disk 50 is set on the turntable 86 while being invertedin case of recording data or reproducing, i.e. the optical disk 50 isset so as to face the surface of the optical disk 50, which the label isto be printed, to the optical pick up 90.

(2) A user edits, on a display of the host computer 133, characters or agraphic image such as a picture to be printed. The host computer 133converts the thus-edited image into image data.

(3) The user instructs to start printing operation on the host computer133.

(4) The spindle motor 88 is stopped in accordance with the instructionoutput from the system control circuit 105 during the course of printingoperation.

(5) The optical pickup 90 is positioned in a predetermined referenceposition.

(6) The laser driver 131 drives the laser diode so that laser power ofthe laser diode of the optical pickup 90 is to be a predetermined lowoutput instructed by the system control circuit 105 (i.e., a value atwhich no changes arise in the visible light characteristic changinglayer and focus control operation can be effected; for example, a valueof 1 mW or less).

(7) In accordance with the instruction output from the system controlcircuit 105, the focus servo circuit 125 is turned on. As a result, thefocus servo circuit 125 performs focus servo operation so that the laserbeam forms the minimum spot on the reflection layer. Here, the trackingservo circuit 127 remains off, and no tracking servo operation iseffected.

(8) Through the foregoing operations, preparation for printing is made,and printing is commenced in accordance with the instruction output fromthe system control circuit 105. That is, the system control circuit 105receives image data from the host computer 133 to drive the feed motor94 to position the optical pickup 90 in a radial position at the innerradius of the optical disk 50, where a first print location is present.The motor 103 (or 119) is driven at the radial position, to move a laserbeam to the direction tangent to a track. In connection with the radialposition on the disk, laser power is switched to a predetermined highoutput (a value at which changes arise in the visible lightcharacteristic changing layer: for example, a value of 1 mW or more)over a print segment in the direction tangent to a track instructed onthe basis of image data. As a result, changes (i.e., discoloration)arise in the reflection characteristic changing layer at the locationexposed to the laser beam of high output power, thereby performing theprinting operation. Then, the feed motor 94 is driven to move theoptical pickup 90 toward an outer circumference at a predetermined pitchΔr, and then with respect to this radial position on the disk, the laserpower is switched to a predetermined high output level over the printsegment in the direction tangent to a track instructed on the basis ofthe image data while the optical pickup 90 is moved in that position inthe direction tangent to a track, thereby performing printing operation.This printing operation sequentially repeated so that the optical pickup90 is moved toward the outer circumference at the predetermined pitchΔr. FIG. 16 shows the locus of movement of the laser beam over the labelsurface 52 of the optical disk 50 through the printing operation and aresultant print product. The laser beam is moved while being vibrated bythe vibration signal, there is produced a print product having no gaps(or having small gaps).

In the present embodiment, the visible light characteristic changinglayer is interposed between a reflection layer and a protective layer.However, the optical disk according to the present invention is notlimited to such a structure. The visible light characteristic changinglayer can be provided in any area (e.g., on a protective layer) viewedfrom a part of a label surface of an optical disk. Although theembodiment has described a case where the optical disk according to thepresent invention having a visible light characteristic changing layerformed integrally is subjected to printing, printing required by thelabel surface printing method and optical disk unit according to thepresent invention is not limited to such printing. More specifically, anoptical disk to which a label having a visible light characteristicchanging layer is affixed can be subjected to printing by application ofthe label surface printing method and optical disk unit according to thepresent invention. In the embodiment, a label surface is subjected toprinting while focus servo operation is being performed. However, whenno request exists for a print resolution, printing can be performedwithout involvement of focus servo operation. In that case, reflectedlight required for effecting focus servo operation is not necessary.Hence, the visible light characteristic changing layer can be formedinto a translucence form so as not to be able to see reflection layerthrough the visible light characteristic changing layer. In theembodiment, printing is performed by using modulating power of the laserbeam in accordance with image data. However, if there are parametersother than power which enable occurrence of changes in the visible lightcharacteristic changing layer by using modulating power in accordancewith image data, printing can be performed by modulating the parameters.The embodiment has described a case where changes arising in the visiblelight characteristic changing layer correspond to discoloration.However, the present invention is not limited to this embodiment. Anytype of change may be employed, so long as the change is visuallyrecognizable. In the embodiment, an optical disk is sequentiallysubjected to printing from its internal circumference to outercircumference. However, the present invention is not limited to such asequence. An optical disk may be sequentially subjected to printing fromits outer to inner circumference, or in another appropriate sequence.The embodiment has described a case where a CD-R disk or CD-RW disk issubjected to printing. However, the present invention can also beapplied to a case where another type of optical disk is subjected toprinting. Moreover, the embodiment has described a case where thepresent invention has been applied to the optical disk unit which isused while being connected to a host computer. However, the presentinvention can be also applied to an optical disk unit which is used in astandalone manner, such as a CD recorder.

1. An apparatus, comprising: an optical pickup; a focus servo coupled toa system controller; a tracking servo coupled to the system controller;and the system controller coupled to the optical pickup to controlrelative movement between the optical pickup and an optical medium, andcoupled to the tracking servo and the focus servo to control thetracking servo and the focus servo, wherein when the optical pickupforms visible information on the optical medium, the controller turnsoff the focus servo and tracking servo, and wherein when the systemcontroller controls the optical pickup to write data on the opticalmedium, the system controller activates the tracking servo and the focusservo while writing data to the optical medium.
 2. The apparatus ofclaim 1, wherein the system controller turns the tracking servo offprior to forming the visible information.
 3. The apparatus of claim 1,wherein the system controller maintains the tracking servo in an offstate prior to forming the visible information.
 4. The apparatus ofclaim 1, wherein the optical medium includes a guide groove which isused while writing data on the optical medium.
 5. The apparatus of claim1, wherein the optical medium includes a guide groove, and the visibleinformation is formed independent of the guide groove.
 6. The apparatusof claim 1, wherein the optical medium is rotated at a constant angularvelocity while the visible information is formed.
 7. The apparatus ofclaim 1, further comprising: a frequency generator coupled to the systemcontroller, wherein the system controller detects a peripheral positionof the optical pickup relative to the optical medium using a signal fromthe frequency generator.
 8. The apparatus of claim 7, furthercomprising: a feed position sensor coupled to the system controller,which detects a radial position of the optical pickup relative to theoptical medium.
 9. The apparatus of claim 1, further comprising: a feedposition sensor coupled to the system controller, which detects a radialposition of the optical pickup relative to the optical medium and adirection tangent to a track of the optical medium.
 10. The apparatus ofclaim 9, wherein the feed position sensor comprises a first feedposition sensor that detects the radial position and a second feedposition sensor that detects the direction tangent to the track.
 11. Theapparatus of claim 1, wherein the system controller turns the focusservo off prior to the forming the visible information.
 12. Theapparatus of claim 1, wherein the system controller maintains the focusservo in an off state prior to the forming the visible information. 13.The apparatus of claim 1, wherein the system controller controls theoptical pickup to write data on the optical medium, wherein the trackingservo and focus servo are active during the data writing.
 14. Theapparatus of claim 1, wherein the optical pickup, system controller andtracking servo are components of an optical disk drive.
 15. Theapparatus of claim 14, wherein the optical disk drive is coupled to acomputer.
 16. The apparatus of claim 14, wherein the optical disk driveis a standalone optical disk recorder.
 17. The apparatus of claim 1,wherein the optical medium has a disk shape.
 18. The apparatus of claim1, wherein the optical medium is a CD-type optical disk.
 19. Theapparatus of claim 1, wherein the optical medium is a DVD-type opticaldisk.
 20. The apparatus of claim 1, wherein the optical pickup heats theoptical medium to form the visible information.
 21. The apparatus ofclaim 1, wherein the optical pickup photosensitizes the optical mediumto form the visible information.
 22. The apparatus according to claim 1,wherein the data is written on a recording layer side of the opticalmedium.
 23. The apparatus according to claim 1, wherein the visibleinformation is formed on a label surface side of the optical medium. 24.A method for forming visible information on an optical medium,comprising the acts of: arranging the optical medium relative to anoptical pickup; and controlling, by a system controller, the opticalpickup to form visible information on the optical medium and to writedata on the optical medium, wherein when the optical pickup forms thevisible information on the optical medium the system controller turnsoff the focus servo and tracking servo, and when the optical pickupwrites data on the optical medium the system controller activates thetracking servo and focus servo.
 25. The method of claim 24, furthercomprising the act of: turning a tracking servo off prior to forming thevisible information.
 26. The method of claim 24, further comprising:maintaining a tracking servo in an off state prior to forming thevisible information.
 27. The method of claim 24, further comprising theact of: writing data on the optical medium using the optical pickup,wherein a tracking servo and focus servo are active during the datawriting.
 28. The method of claim 27, wherein the optical medium includesa guide groove which is used while writing data on the optical medium.29. The method of claim 27, wherein the optical medium includes a guidegroove, and the visible information is formed independent of the guidegroove.
 30. The method of claim 24, wherein the optical medium isrotated at a constant angular velocity while the visible information isformed.
 31. The method of claim 24, further comprising the act of:detecting a peripheral position of the optical pickup relative to theoptical medium using a signal from a frequency generator.
 32. The methodof claim 24, further comprising the act of: detecting, by a feedposition sensor, a radial position of the optical pickup relative to theoptical medium.
 33. The method of claim 24, further comprising the actof: detecting, by a feed position sensor, a radial position of theoptical pickup relative to the optical medium and a direction tangent toa track of the optical medium.
 34. The method of claim 33, wherein afirst feed position sensor detects the radial position and a second feedposition sensor detects the direction tangent to the track.
 35. Themethod of claim 24, further comprising the act of: turning the focusservo off prior to forming the visible information.
 36. The method ofclaim 24, further comprising the act of: maintaining the focus servo inan off state prior to forming the visible information.
 37. The method ofclaim 24, wherein the optical medium has a disk shape.
 38. The method ofclaim 24, wherein the optical medium is a CD-type optical disk.
 39. Themethod of claim 24, wherein the optical medium is a DVD-type opticaldisk.
 40. The method of claim 24, wherein the optical pickup heats theoptical medium to form the visible information.
 41. The method of claim24, wherein the optical pickup photosensitizes the optical medium toform the visible information.
 42. The method according to claim 24,wherein the data is written on a recording layer side of the opticalmedium.
 43. The method according to claim 24, wherein the visibleinformation is formed on a label surface side of the optical medium.